Contra Costa County, CA Building Setbacks & Zoning: Setback Rules (2026)
Key Facts
- Front setback
- 20 ft minimum for any R-6 structure
- Corner lot
- 20 ft principal frontage, 15 ft secondary frontage
- Side yard
- 15 ft aggregate, no side under 5 ft
- Accessory side yard
- Reduced to 3 ft if 50 ft from front line
- Rear yard
- 15 ft for main house, 3 ft for accessory
- Variance path
- Chapters 26-2 and 82-6
Summary
In the R-6 single-family district, the county's base residential zone for unincorporated Contra Costa County, every structure needs a 20-foot front setback, an aggregate 15-foot side yard with no single side under 5 feet, and a 15-foot rear yard for the main house. Accessory buildings get reduced minimums under Ordinance Code Sections 84-4.1002, 84-4.1004, and 84-4.1006.
84-4.1002 - Yard—Side. There shall be an aggregate side yard width of at least fifteen feet. No side yard shall be less than five feet wide. These minima may be reduced to three feet for an accessory building or structure if it is set back at least fifty feet from the front property line. 84-4.1004 - Yard—Setback. There shall be a setback (front yard) of at least twenty feet for any structure in the R-6 district. On corner lots the principal frontage shall have a setback of at least twenty feet and the other setback shall be at least fifteen feet. 84-4.1006 - Yard—Rear. There shall be a rear yard for any principal structure of at least fifteen feet. There shall be a rear yard for accessory structures of at least three feet.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Ordinance Code: Supplement 103).
Full Breakdown
Contra Costa County zones most unincorporated single-family neighborhoods R-6 through R-100, with R-6 (six-thousand-square-foot minimum lots) the county's most common base district. 10 sets the yard standards that apply to every structure built in an R-6 district. The front setback is a flat 20 feet, and on corner lots the county requires the full 20-foot setback along the principal frontage while permitting the secondary street-facing yard to shrink to 15 feet. Side yards must total at least 15 feet in aggregate, with no single side yard narrower than 5 feet; that minimum drops to just 3 feet for an accessory building or structure, but only if it sits at least 50 feet back from the front property line.
The rear yard for the main house must be at least 15 feet, while detached accessory structures like sheds or garages need only 3 feet of rear yard clearance. 10, and so on through R-100, each keyed to that district's larger minimum lot size but following the identical front, side, and rear yard structure. A property owner who cannot meet these minimums, for example on an older, narrower lot, can apply for a variance under Chapters 26-2 and 82-6 rather than build out of compliance. The Department of Conservation and Development checks setback compliance at permit review and again at foundation inspection before framing begins.
Violations & Fines
Building or expanding a structure that encroaches into a required front, side, or rear setback is a zoning code violation under Section 82-2.006, which treats any structure erected, constructed, altered, or maintained contrary to Title 8 as unlawful and a public nuisance. Code enforcement can require removal or relocation of the encroaching portion, and the county may pursue any other remedy allowed under the code or state law to bring the property into compliance.
Frequently Asked Questions
What is the minimum front yard setback in Contra Costa County's R-6 zone?
How close to my side property line can I build?
Do these setbacks apply outside the R-6 district too?
Sources & Official References
Other rules in Contra Costa County
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